O’Reilly Automotive Inc. ( ORLY - Analyst Report ) announced that its Board of Directors has approved a resolution to boost the authorization under its share repurchase program by an additional $500 million. The additional authorization, beginning on August 10, 2012, is effective for 3 years.

During the first half of the year, the company repurchased 6.3 million shares at an average price of $94.52, reflecting a total investment of $594 million. Subsequent to the end of the second quarter until July 25, 2012, it repurchased an additional 3.1 million shares at an average price of $85.48, implying a total investment of $267 million.

Since the inception of the share repurchase program in January 2011 until July 25, 2012, O’Reilly has repurchased 25.3 million shares at an average price of $72.67, reflecting a total investment of $1.84 billion.

The company last increased the authorization under the repurchase program by an additional $500 million on June 1, 2012. With the additional authorization of $500 million, the cumulative authorization under the program went up to $2.5 billion.

The company earned $1.15 per share in the second quarter of 2012, a robust 20% increase from 96 cents in the last year quarter and inched past the Zacks Consensus Estimate by a penny. Net income increased 9% to $146 million (9.3% of sales) from $134 million (9.0%) in the second quarter of 2011.

Sales for the quarter rose 6% to $1.56 billion from $1.48 billion a year ago, almost in line with the Zacks Consensus Estimate of $1.57 billion. Comparable store sales (change in sales for stores open at least one year) scaled up 2.5% compared with 4.4% in the second quarter of 2011.

O’Reilly has projected earnings per share of $1.25 to $1.29 and consolidated comparable store sales to increase in the range of 1% to 3% for the third quarter of the year. For full year 2012, the company anticipates earnings per share in the range of $4.56 to $4.66 and consolidated comparable store sales to increase by 3% to 5%. This compared with the previous guidance of $4.47–$4.57 and 3% to 6%.

The company reiterated its revenue guidance of $6.15 billion–$6.25 billion, gross margin guidance of 49.4%–49.8% and operating margin guidance of 15.4%–15.9% for the year. It has also reiterated its capital expenditures guidance of $315 million to $345 million but raised free cash flow guidance to $725 million to $775 million from $700 million to $750 million for the year.

O'Reilly, a Zacks #3 Rank (Hold) stock, is the third largest specialty retailer of automotive aftermarket parts, tools, supplies, equipment, and accessories in the U.S., selling products to both Do-it-Yourself (DIY) customers and Do-it-for-Me (DIFM) or professional installers. Its main competitors include Advance Auto Parts Inc. ( AAP - Analyst Report ) , AutoZone Inc. ( AZO - Analyst Report ) and Pep Boys - Manny, Moe & Jack ( PBY - Snapshot Report ) .